Energy conservation and environmental protection is a basic national policy of China. 600,000 tones of printing ink (dye) are consumed by the printing industry per year in China. The printing ink is discharged into the nature and causes pollution for lack of effective treatment measures. Hence, it is emergent to reduce the conservation of the printing ink in the printing industry and to promote the innovation of green printing technologies.
A method for producing a colorful layer on the surface of a base material by using resonance characteristics of a Fabry-Perot resonant cavity is provided in the Chinese patent application No. CN200480042867. As shown in FIG. 1, the Fabry-Perot resonant cavity 100 includes: a total-reflective metallic layer 101, a transflective metallic layer 103, and a medium layer 102 provided between them. The resonance frequency of the whole Fabry-Perot resonant cavity may be in accordance with the frequency of specific light wave by adjusting the thickness of the medium layer 102. The specific light wave is absorbed through resonance and a colorful effect is produced on the surface. This patent application records the Fabry-Perot resonant cavity as only a monochromatic filter, but does not mention the production of colorful images or complicated colors. In addition, batch and low-cost production of colorful image are desirable for commercial production of ink-free printed products.